Tums are generally safe for occasional heartburn relief, but they do come with side effects, especially if you use them frequently or in large amounts. The active ingredient, calcium carbonate, neutralizes stomach acid on contact, but it also introduces a significant dose of calcium into your body and triggers changes in your digestive system that can cause problems over time.
Common Side Effects
Most people who take Tums occasionally won’t notice anything beyond mild digestive discomfort. The most frequently reported side effects include constipation, stomach pain, belching, and nausea or vomiting. Some people also experience dry mouth, a metallic taste, or increased urination.
The belching and bloating have a straightforward explanation. When calcium carbonate meets hydrochloric acid in your stomach, the reaction produces carbon dioxide gas, water, and calcium chloride. That carbon dioxide is what makes you burp. Constipation is also common because calcium slows down the movement of food through your intestines. For most people, these effects are mild and go away on their own.
Acid Rebound: The Backfire Effect
One of the more frustrating side effects of Tums is something called acid rebound. After the antacid neutralizes your stomach acid and wears off, your stomach can respond by producing even more acid than it did before you took the tablet. Research published in the New England Journal of Medicine found that calcium carbonate specifically stimulates additional gastric acid secretion, and this effect is made worse by the presence of food. So if you’re taking Tums with meals, the rebound can be more pronounced.
This creates a cycle where you feel temporary relief, then worse heartburn, then reach for more Tums. If you find yourself needing antacids daily for more than two weeks, that pattern itself is a signal that something else is going on and a different treatment approach may work better.
Too Much Calcium: Hypercalcemia
Each Tums tablet delivers a concentrated dose of calcium. If you take several tablets a day over weeks or months, you can push your blood calcium levels too high, a condition called hypercalcemia. Early signs include nausea, loss of appetite, increased thirst, and constipation that gets progressively worse. As levels climb higher, you may experience confusion, irritability, muscle twitching, headaches, or fatigue. In severe cases, hypercalcemia can cause irregular heartbeat.
The NIH sets daily upper limits for total calcium intake from all sources (food, drinks, and supplements combined) at 2,500 mg for adults 19 to 50 and 2,000 mg for adults over 51. A single extra-strength Tums tablet contains 750 mg of calcium carbonate, so it doesn’t take many tablets on top of a normal diet to approach those limits. Pregnant and breastfeeding women, who sometimes use Tums for both heartburn and calcium supplementation, have the same 2,500 mg ceiling.
Milk-Alkali Syndrome
The most serious complication from chronic Tums overuse is milk-alkali syndrome, a condition defined by three simultaneous problems: high blood calcium, kidney damage, and a shift in blood chemistry toward being too alkaline. It was first described in the 1940s in patients who were treating ulcers with large amounts of milk and antacids, but it still occurs today, typically in people who consume excessive calcium carbonate over a prolonged period.
Symptoms overlap with general hypercalcemia (nausea, confusion, weakness) but also include bone pain, depression, and in extreme cases, calcium deposits in soft tissues like the lungs or under the skin. Kidney function can deteriorate significantly. The condition is reversible if caught early, but it requires medical treatment and stopping the calcium source.
Kidney Stone Risk
Calcium is a major component of about 85% of kidney stones, usually in the form of calcium oxalate or calcium phosphate. While dietary calcium from food actually tends to protect against stones, supplemental calcium tells a different story. Data from a large cohort of women found that those taking even modest calcium supplements had a 20% higher relative risk of forming kidney stones compared to women who took no supplements. The 37% increase in kidney stone prevalence among American women between the late 1970s and early 1990s has been linked to the rise in calcium supplement use during that same period.
This doesn’t mean a few Tums will give you kidney stones. The risk grows with regular, sustained use, particularly if you’re not drinking enough water or you’re already prone to stones.
Interference With Other Medications
Calcium carbonate can reduce how well your body absorbs certain medications. Iron supplements are one of the most common interactions. Calcium binds to iron in the digestive tract, preventing your body from taking it up efficiently. The same principle applies to certain antibiotics and medications used to treat osteoporosis. If you take any prescription medications regularly, spacing them at least two hours apart from Tums helps minimize this effect.
The interaction works both ways in some cases. By raising the pH of your stomach contents, Tums can change how quickly some drugs dissolve and enter your bloodstream. This is particularly relevant for medications that depend on an acidic stomach environment to be absorbed properly.
Use in Children
Children’s versions of Tums exist, but dosing is much more restricted. Kids ages 2 to 5 should take no more than 3 tablets in 24 hours, while children ages 6 to 11 are limited to 6 tablets per day. Children under 2 should not take Tums without a doctor’s guidance. For any child, use beyond two weeks at maximum dosage needs medical supervision. The same drug interaction concerns apply to children, so if your child takes any prescription medication, check before adding an antacid.
Who Should Be Extra Cautious
People with a history of kidney stones or kidney disease face amplified risks from regular Tums use, since their kidneys are already less efficient at clearing excess calcium. Anyone with hyperparathyroidism, a condition where the parathyroid glands overproduce hormones that regulate calcium, is working with already elevated calcium levels, and adding more through antacids can worsen the imbalance. Research on calcium supplementation in people with hyperparathyroidism has shown mixed results, with some studies finding it actually suppresses the overactive hormone and others finding no effect, so the picture is complicated enough that it warrants a conversation with your doctor before using Tums regularly.
People who are prone to constipation, those on low-sodium diets, or anyone already taking calcium supplements for bone health should also pay close attention to their total daily calcium intake rather than treating Tums as a harmless candy-like tablet.